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A227484
The Wiener index of the dendrimer D_4[n], defined pictorially in the A. R. Ashrafi et al. reference.
1
426, 110582, 1543242, 12208658, 76176642, 419676194, 2147525346, 10478078306, 49478563938, 228185184866, 1033790121570, 4619196304994, 20412418326114, 89390811225698, 388524258582114, 1677932514369122, 7207051830287970, 30809448121032290, 131162651106926178, 556349805776789090, 2352195514241310306
OFFSET
0,1
COMMENTS
a(1) has been checked by the direct computation of the Wiener index (using Maple).
REFERENCES
A. R. Ashrafi and H. Shabani, Computing Padmakar-Ivan index of four classes of dendrimers, Bulgarian Chem. Comm., 44, N0. 2, 2012, 127-130.
FORMULA
a(n) = -74142 + 2^n*(241658-45756*n)+4^n*(115320*n - 167090).
G.f.: 2*(213 +52522*z + 66470*z^2 -419644*z^3-33200*z^4)/((1-z)*(1-2*z)^2*(1-4*z)^2).
MAPLE
a := proc (n) options operator, arrow: -74142+2^n*(241658-45756*n)+4^n*(115320*n-167090) end proc: seq(a(n), n = 0 .. 20);
CROSSREFS
Sequence in context: A236699 A338154 A173374 * A272131 A054984 A251147
KEYWORD
nonn
AUTHOR
Emeric Deutsch, Jul 13 2013
STATUS
approved